CurtPalme.com Home Theater Forum

Enri · Joined: 19 Jul 2006 Posts: 17

someboy knows what's going on with those marquee 9" tubes ?!?

PaulB · Posted: Sat Dec 08, 2007 12:24 pm Post subject:

Exact same problem and answer here - https://www.curtpalme.com/forum_archived/viewtopic.php@t=7361.html

Paul

Enri · Joined: 19 Jul 2006 Posts: 17

paul,
I read the thred but pics are bad and I can't see your crt problem ... anyway on my tubes looks like fingerprints on c elements, and reading the formum I was thinking it can be fungus ...
did you changed c elements to resolve?

PaulB · Posted: Sat Dec 08, 2007 1:46 pm Post subject:

Sorry for the bad pictures, done in haste I'm afraid.

The stuff I have looks like little greyish white globs / particles and that pretty much looks to be what I'm seeing in your pictures. Its corrosion/reaction between the glycol and the interior of the LC chamber - probably from the screws and aluminium hardware (see how the globs line up with the bleed screw directly above). If you shake the tube a bit you should see the stuff move around. Luckily for me it only affects one tube but I will be removing the C-Element to clean out the chamber, primarily because the corrosion stuff has left a trail down the inside of the C-Element so I need to remove it to clean it and the chamber.

I've seen this problem on a few marquees now, seems to be a disease! Came as a shock to me when I first saw it in m y own 9500 Shocked

Can be prevented (or at least reduced) by either putting in stainless steel bleed screws (easy) or coating the ends of the existing screws with silicone (not too keen on this ).

I think once you have the globs, you really have to do something about it sooner or later. Cleaning out the affected chamber and replacing all the LC bleed screws in all the tubes for stainless steel ones is what I am about to do shortly.
Paul

messerfloh · Joined: 04 Dec 2007 Posts: 18 Location: Bavaria, Germany

Hi all, my first post here Very Happy

! Great forum, congrats!!

just my 2cents: when you have contact corrosion (= 2 different metals plus an electrolyte like glycol) you won´t solve the problems by replacing the bloody bleeding screw with stainless steel. You again have two different metals, worse stainless steel has a higher electrochemical potential than normal steel screws. This means the corrosion would take place again, just faster!
So, use ALUMINUM screws! Since they do not have to bear any mechanical stress, alu will do, I think.

Servus!
Floh

PaulB · Posted: Sun Dec 09, 2007 2:21 pm Post subject:

Hi Enri,

Well, I just spent a few hours cleaning my green LC chamber which was badly affected by the corrosion/globs. The C-Element unfortunately is siliconed tight as has been reported by others so I had to resort to cleaning the LC chamber by flushing it out through the bleed holes. (As an aside, its interesting that the green tube always looks to be the most badly corroded one in all the pictures I've seen)

First, I drained the glycol using a syringe and heat-shrink tubing. Took a while but easy to do (just be careful when you remove the bleed screws as the glycol may spurt out). I then half-filled the chamber with water, sloshed that around and then drained the chamber by turning the tube upside down and shaking it. This was done about 4 or 5 times and removed about 50% of the globs. I then put in some warm water which had a small drop of washing-up liquid in it. Again I half-filled the chamber, shook it about then drained it - this single flush probably cleared about another 45% of the globs in one go! After this I just flushed the tube with clean water a couple more times and set it aside to dry. At the end about 99% of the crud/globs had been removed so its well worth doing.

However! I had a further related issue not so easily resolved. There were streaks on the inside of the C-Element and on the tube face that came from the corroding screws and these marks were still visible after flushing and clearly quite bad. I then decided to take the bull by the horns and cut out the bellows so that I could inspect the marks closer and see if I could remove them!

I cut the bellows out quite easily and on removing the front hardware with the detached bellows, I was astonished at just how dirty the tube face actually was! A quick clean restored the tube face and the C-Element to their former pristine condition but the amount of dirt and staining (obviously stemming from the screws) was incredible. OK, I need a new bellows now but the cost is well worth it for the difference in the newly cleaned tube face and c-element !! Unfortunately I didn't take any before and after pictures but believe me, the tube face was absolutely manky (manky, do you use this word in the US? = filthy dirty). The stain marks were so bad that it actually looked like the tube had 4:3 burn-in !

A close inpection of the screw holes revealed a few small globs in the process of being formed (like little grey air bubbles attached to the side of the screwholes).

Heres a picture of the screwhole thats causing the chamber contamination. I'd wiped the globs off before the picture was taken. Nasty eh! Not sure how to actually fix that.

Paul

PaulB · Posted: Sun Dec 09, 2007 2:31 pm Post subject:

PaulB · Posted: Sun Dec 09, 2007 3:18 pm Post subject:

Bellows removed

Is it worth cleaning off the residual silicone or just leave it as is (will be covered by a fresh layer once new bellows is installed)? Edit - started removing the old silicone with a razor
Paul

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Funny I have three Barcos and none have had this problem. Even the one I bought with 10K on the tubes ?

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

foobar, they don't make aluminum screws and for a good reason. Use screws made of 316 ultra corrosion resistant stainless steel and and give them a light coating of PTFE thread sealant. Use loctite 567 solven resistant formula. Allow it cure before re-filling chamber.

PaulB · Posted: Sun Dec 09, 2007 5:06 pm Post subject:

messerfloh · Joined: 04 Dec 2007 Posts: 18 Location: Bavaria, Germany

Hi Paul,
don´t know where to get aluminum screws in UK. Maybe also plastic (e.g. polyamide = nylon) screws would serve, too.
My idea is just to replace the screws with a material that has the same electrochemical properties as the frame of the tube. Or with an electrochemically inert material like nylon. Stainless steel contains nickel and chromium (among other elements) which are more "noble" (in the chemical sense) than the aluminum frame, so again corrosion will take place. In this case the auminum will corrode since it is less noble.

Also Dragan is right suggesting the use of a sealant (don´t know whether that Locktite stuff can stand the glycol?). Maybe you could even use the same silicone that you use for sealing the tube faceplate anyway.

For the proper size of that particular screw, just take the old ones to a good hardware dealer or tool shop (well wherever they sell screws in the UK Wink

) and show them to the clerk, he should find out. If not , leave!!! bad shop!!! Here in Germoney they sell alu screws in motorcycle shops, they come anodized in various colors which the bike maddies like for pimping their streetfighters.

to that corrosion issue i have a funny story about my grandpa: he wanted to fix the roof gutter (copper!) with those easy to use pop-rivets. fast repair, but the rivets were from aluminum. 4 or 5 weeks later they were gone due to corrosion! gutter still pouring... Evil or Very Mad

So, good luck anyway!
I´m going back to the vault to play with my new mate (IGOR!! Bring me another brain, willya! UAHAHA Evil or Very Mad

).
Results to be posted...

Greetz Floh

PaulB · Posted: Fri Mar 14, 2008 8:52 am Post subject:

Clarence · Posted: Fri Mar 14, 2008 12:02 pm Post subject:

aspec2 · Joined: 10 Apr 2006 Posts: 549

Paul

Wish I'd seen this thread before we conversed. I would have got you nylon instead of stainless. Still can if you like.

Walt